mysql> show variables like 'character_set_database';

mysql> show create table <表名>;

mysql>create database <数据库名> character set utf8;

create table tb_books (
 name varchar(45) not null,
 price double not null,
 bookCount int not null,
 author varchar(45) not null ) default charset = utf8;

mysql>alter database <数据库名> character set utf8;

mysql>alter table <表名> character set utf8;

mysql>alter table <表名> change <字段名> <字段名> <类型> character set utf8;

mysql>alter table user change username username varchar(20) character set utf8 not null;

mysql>alter table tb_product add constraint fk_1 foreign key(factoryid) references tb_factory(factoryid);
mysql>alter table <表名> add constraint <外键名> foreign key<字段名> REFERENCES <外表表名><字段名>;

mysql>alter table tb_people drop foreign key fk_1;
mysql>alter table <表名> drop foreign key <外键名>;